Worm-gearing.



. PATENTED JULY 14, 1908.

- E. B. SWEET.

WORM GEARING.

APPLICATION FILED JAN. 11, 190B.

2 SHEETS-SHBET 1 llllllll I' l W21 tn esse PATENTED' JULY 14, 1908.

E. E. SWEET. WORM GEARING. APPLICATION FILED JAN.11, 1908 2 SHEETS-SHEET2.

7 WI fn ess es 7 lm e'n for I 5m estE'u/qef. I .5; MM I UNITED STATESPATENT ormcn ERNEST E. SWEET, or DETROIT, MICHIGAN, ASSIGNOR To CADILLACMOTOR OAR COMPANY, or nn'rnorr, MICHIGAN, A CORPORATION or MICHIGAN.

' WORM-GEARING.

" Specification of Letters Patent.

Patented July 14, 1908.

Application filed January 11, 1908. Serial N 0. 410,439.

To all whom it may concern:

citizen of the United States of America,

residing at Detroit, in the county of Wayne and State of Michi an, haveinvented certain new and useful mprovements in Worm- Gearing, of whichthe following is a specification, reference being had therein to theaccompanying drawings. a

The inventlon relates to that type of steering ear in which rotation ofthe steering whee and stem is transmitted through the medium of a gearto a transversely-extending' rock shaft, arid from the latter to themechanism for turning the wheels. In order that the. vehicle may beturned in a small space, it is necessary to provide a gear segment whichmay be adjusted through a relatively lar e angle but in the ordinaryoperation of t 1e apparatus, where the vehicle is merely guided in asubstantially straight course, the angular movement imparted to the gearis veryslight. As a consequence, the wear in the gear teeth is chieflylimited to the central portion of the segment, and it is in this portionthat it is most desirable to take up all lost motion, so that thevehicle angl will respond quickly to any movement of the steering wheel.Adjustment for taking up the lost motion is a simple matter, merelyrequiring the movement of the shaft on which the ear segment is mountedtowards the axis 0 the cooperating gear member, but it is obvious thatif such adjustment is made, to take up wear, limited to the centralortionof the gear segment, it will cause the inding of the'teeth onopposite sides of this central portion when the gear is moved through a.greater angle, thus rendering the gear practically ino erative; Theresent invention is designer to overcome this difficulty by providingaconstruction in which adjustment may be made to compensate for wear inthe central portion of the gear without interferingwith theoperativeness of the apparatus when moved through a greater To this endthe invention consists in a construction of worm gear which initially isprovided with a slight clearance for the teeth of the outerportions ofthe segment when the axis of the gear shaft is properly adjusted to takeu all lost motion in the central portion oft "e segment. ."With such aconstruction, when the central portion of ciple of 'onstruction thereof;and Figs. 3

and 4 are similar views illustrating modifications.

A is the rotary steering stem and B is the worm member mounted u on thisstem and preferably within a suitab e housing 0.

,D is the worm gear, which is mounted upon the rock shaft E, and thelatter is adjustably mounted in the casing preferably by being journaledin eccentric bearings F therein. In the cutting of the teeth on the gearsegment D, instead of adjusting the center of rotation to coincide withthe axis G of the rock shaft IE, it is adjusted to turn from a center Hupon a sli htly lesser radius. This will result 1n provi ing a slightclearance for the teeth at o po'site ends of the segment D which graduay diminishes as the center of the. segment is approached, and thus there quired-adjustment for wear in the central portion of the segment isat any time permissibleQ With the constructiondescribed, adjustment maybe made by any user of the machine without requiring the exercise ofspecial mechanical skill. Furthermore, the wear in the gear tends torender it more rather than less perfect for it enlar es the segment inwhich the teeth are in ful mesh. The slight play between the teeth atthe ends of the segment and the worm is immaterial for these partsareonly in engagement whenthe steering wheels of the vehicle are turned ata decided angle, and at such times the re sistance of the wheels willkeep the worm and gear in contact. On the other hand, where there is anyplay at the center of the gear there will be constant vibration andrattling, as there is no resisting force to hold the parts in contact.

The, adjustments which are provided in steering gears not constructed inaccordance with my invention are only serviceable for factory'adjustmentthat is, for originally setting the gears in proper placebefore they have been in use, but after wear such adjustments cannot beused for the reasons already set forth.

seeps-2 In Figs. 3 and. t modified constructions are illustrated, theformer showing a pinion I. engaging e rack J, the teeth of which areslightly deflected from a straight line. I Fig. 4 s segmental rack,similar to that illustratedin Fig. 2, is employed, but is arranged toengage a straight gear or pinion K, instead oi the worm gear; Both ofthese constructions comedy the same principle the constructionsillustrated in Figs. 1 and 2, Yl'zi, that the central portion of therack has its teeth slightly in advance of the end portions thereof.

Vw hilc the present construction especially adapted for the steeringmechanism of motor venicles, it is not, however, necessarily timited tosuch aeombina-tion, as it will be ohserved. that it can readily beadapted for various uses in other gear constructions, and also that thedesign and construction of the gearing may be varied without departing*rom my invention.

What i claim. as myinvention is:

1. in a gearing, cooperating interineshing members constructed toprovide a slight clearance between the intermeshing portions thereofwhen moved from the normal position, while being in full engagement atthe normal position.

2. In a gearing, cooperating intermeshing members constructed to providea slight clearance when moved in either direction from the normalposition while being in full engagement at the central or normalposition. 3. in a gearing, cooperating gear memhers, the pitch line ofthe teeth of one of said members having a dillerent radius than the axisof rotation of said gear, for the purpose described. 40 4. A wormgearing, the pitch line of the teeth of the gear member thereof having adill'erent radius than the axis of rotation of said gear, for thepurpose described.

5. in a gearing, cooperating intermeshing memhers constructed to providea slight clearance between the intermeshing portions thereof when movedfrom the normal position, while being in full engagement at the normalposition, and means for ad'usting the relation of said cooperatingmembers.

6. In agearing, cooperating gen-r members, the pitch line of the teethof one of said members having a different radius than the axis ofrotation of said gear, and means for adjusting the relation 01 thecenters of said radii, for the purpose described.

In testimony whereof I afiix my signature in presence of two witnesses.

ERNEST E. SWEET Witnesses:

AMELIA WILLIAMs, NELLIE KmsELLA.

